--- /dev/null
+#
+# Copyright 2005,2006 Free Software Foundation, Inc.
+#
+# This file is part of GNU Radio
+#
+# GNU Radio is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3, or (at your option)
+# any later version.
+#
+# GNU Radio is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with GNU Radio; see the file COPYING. If not, write to
+# the Free Software Foundation, Inc., 51 Franklin Street,
+# Boston, MA 02110-1301, USA.
+#
+
+from gnuradio import gr
+from gnuradio.blks2impl.fm_emph import fm_deemph
+import math
+
+class wfm_rcv_pll(gr.hier_block2):
+ def __init__ (self, demod_rate, audio_decimation):
+ """
+ Hierarchical block for demodulating a broadcast FM signal.
+
+ The input is the downconverted complex baseband signal (gr_complex).
+ The output is two streams of the demodulated audio (float) 0=Left, 1=Right.
+
+ @param demod_rate: input sample rate of complex baseband input.
+ @type demod_rate: float
+ @param audio_decimation: how much to decimate demod_rate to get to audio.
+ @type audio_decimation: integer
+ """
+ gr.hier_block2.__init__(self, "wfm_rcv_pll",
+ gr.io_signature(1, 1, gr.sizeof_gr_complex), # Input signature
+ gr.io_signature(2, 2, gr.sizeof_float)) # Output signature
+ bandwidth = 250e3
+ audio_rate = demod_rate / audio_decimation
+
+
+ # We assign to self so that outsiders can grab the demodulator
+ # if they need to. E.g., to plot its output.
+ #
+ # input: complex; output: float
+ alpha = 0.25*bandwidth * math.pi / demod_rate
+ beta = alpha * alpha / 4.0
+ max_freq = 2.0*math.pi*90e3/demod_rate
+
+ self.fm_demod = gr.pll_freqdet_cf (alpha,beta,max_freq,-max_freq)
+
+ # input: float; output: float
+ self.deemph_Left = fm_deemph (audio_rate)
+ self.deemph_Right = fm_deemph (audio_rate)
+
+ # compute FIR filter taps for audio filter
+ width_of_transition_band = audio_rate / 32
+ audio_coeffs = gr.firdes.low_pass (1.0 , # gain
+ demod_rate, # sampling rate
+ 15000 ,
+ width_of_transition_band,
+ gr.firdes.WIN_HAMMING)
+ # input: float; output: float
+ self.audio_filter = gr.fir_filter_fff (audio_decimation, audio_coeffs)
+ if 1:
+ # Pick off the stereo carrier/2 with this filter. It attenuated 10 dB so apply 10 dB gain
+ # We pick off the negative frequency half because we want to base band by it!
+ ## NOTE THIS WAS HACKED TO OFFSET INSERTION LOSS DUE TO DEEMPHASIS
+
+ stereo_carrier_filter_coeffs = gr.firdes.complex_band_pass(10.0,
+ demod_rate,
+ -19020,
+ -18980,
+ width_of_transition_band,
+ gr.firdes.WIN_HAMMING)
+
+ #print "len stereo carrier filter = ",len(stereo_carrier_filter_coeffs)
+ #print "stereo carrier filter ", stereo_carrier_filter_coeffs
+ #print "width of transition band = ",width_of_transition_band, " audio rate = ", audio_rate
+
+ # Pick off the double side band suppressed carrier Left-Right audio. It is attenuated 10 dB so apply 10 dB gain
+
+ stereo_dsbsc_filter_coeffs = gr.firdes.complex_band_pass(20.0,
+ demod_rate,
+ 38000-15000/2,
+ 38000+15000/2,
+ width_of_transition_band,
+ gr.firdes.WIN_HAMMING)
+ #print "len stereo dsbsc filter = ",len(stereo_dsbsc_filter_coeffs)
+ #print "stereo dsbsc filter ", stereo_dsbsc_filter_coeffs
+ # construct overlap add filter system from coefficients for stereo carrier
+
+ self.stereo_carrier_filter = gr.fir_filter_fcc(audio_decimation, stereo_carrier_filter_coeffs)
+
+ # carrier is twice the picked off carrier so arrange to do a commplex multiply
+
+ self.stereo_carrier_generator = gr.multiply_cc();
+
+ # Pick off the rds signal
+
+ stereo_rds_filter_coeffs = gr.firdes.complex_band_pass(30.0,
+ demod_rate,
+ 57000 - 1500,
+ 57000 + 1500,
+ width_of_transition_band,
+ gr.firdes.WIN_HAMMING)
+ #print "len stereo dsbsc filter = ",len(stereo_dsbsc_filter_coeffs)
+ #print "stereo dsbsc filter ", stereo_dsbsc_filter_coeffs
+ # construct overlap add filter system from coefficients for stereo carrier
+
+ self.rds_signal_filter = gr.fir_filter_fcc(audio_decimation, stereo_rds_filter_coeffs)
+
+
+
+
+
+
+ self.rds_carrier_generator = gr.multiply_cc();
+ self.rds_signal_generator = gr.multiply_cc();
+ self_rds_signal_processor = gr.null_sink(gr.sizeof_gr_complex);
+
+
+
+ alpha = 5 * 0.25 * math.pi / (audio_rate)
+ beta = alpha * alpha / 4.0
+ max_freq = -2.0*math.pi*18990/audio_rate;
+ min_freq = -2.0*math.pi*19010/audio_rate;
+
+ self.stereo_carrier_pll_recovery = gr.pll_refout_cc(alpha,beta,max_freq,min_freq);
+ #self.stereo_carrier_pll_recovery.squelch_enable(False) #pll_refout does not have squelch yet, so disabled for now
+
+
+ # set up mixer (multiplier) to get the L-R signal at baseband
+
+ self.stereo_basebander = gr.multiply_cc();
+
+ # pick off the real component of the basebanded L-R signal. The imaginary SHOULD be zero
+
+ self.LmR_real = gr.complex_to_real();
+ self.Make_Left = gr.add_ff();
+ self.Make_Right = gr.sub_ff();
+
+ self.stereo_dsbsc_filter = gr.fir_filter_fcc(audio_decimation, stereo_dsbsc_filter_coeffs)
+
+
+ if 1:
+
+ # send the real signal to complex filter to pick off the carrier and then to one side of a multiplier
+ self.connect (self, self.fm_demod,self.stereo_carrier_filter,self.stereo_carrier_pll_recovery, (self.stereo_carrier_generator,0))
+ # send the already filtered carrier to the otherside of the carrier
+ self.connect (self.stereo_carrier_pll_recovery, (self.stereo_carrier_generator,1))
+ # the resulting signal from this multiplier is the carrier with correct phase but at -38000 Hz.
+
+ # send the new carrier to one side of the mixer (multiplier)
+ self.connect (self.stereo_carrier_generator, (self.stereo_basebander,0))
+ # send the demphasized audio to the DSBSC pick off filter, the complex
+ # DSBSC signal at +38000 Hz is sent to the other side of the mixer/multiplier
+ self.connect (self.fm_demod,self.stereo_dsbsc_filter, (self.stereo_basebander,1))
+ # the result is BASEBANDED DSBSC with phase zero!
+
+ # Pick off the real part since the imaginary is theoretically zero and then to one side of a summer
+ self.connect (self.stereo_basebander, self.LmR_real, (self.Make_Left,0))
+ #take the same real part of the DSBSC baseband signal and send it to negative side of a subtracter
+ self.connect (self.LmR_real,(self.Make_Right,1))
+
+ # Make rds carrier by taking the squared pilot tone and multiplying by pilot tone
+ self.connect (self.stereo_basebander,(self.rds_carrier_generator,0))
+ self.connect (self.stereo_carrier_pll_recovery,(self.rds_carrier_generator,1))
+ # take signal, filter off rds, send into mixer 0 channel
+ self.connect (self.fm_demod,self.rds_signal_filter,(self.rds_signal_generator,0))
+ # take rds_carrier_generator output and send into mixer 1 channel
+ self.connect (self.rds_carrier_generator,(self.rds_signal_generator,1))
+ # send basebanded rds signal and send into "processor" which for now is a null sink
+ self.connect (self.rds_signal_generator,self_rds_signal_processor)
+
+
+ if 1:
+ # pick off the audio, L+R that is what we used to have and send it to the summer
+ self.connect(self.fm_demod, self.audio_filter, (self.Make_Left, 1))
+ # take the picked off L+R audio and send it to the PLUS side of the subtractor
+ self.connect(self.audio_filter,(self.Make_Right, 0))
+ # The result of Make_Left gets (L+R) + (L-R) and results in 2*L
+ # The result of Make_Right gets (L+R) - (L-R) and results in 2*R
+ self.connect(self.Make_Left , self.deemph_Left, (self, 0))
+ self.connect(self.Make_Right, self.deemph_Right, (self, 1))
+ # NOTE: mono support will require variable number of outputs in hier_block2s
+ # See ticket:174 in Trac database
+ #else:
+ # self.connect (self.fm_demod, self.audio_filter, self)
projects / debian / gnuradio / blobdiff